Biomechanical Effect of Using Cement Augmentation to Prevent Proximal Junctional Kyphosis in Long-Segment Fusion: A Finite Element Study

PurposeThe purpose of this study was to compare the biomechanical effects of cement-reinforced vertebrae at different levels and with different volumes of cement in preventing proximal junction kyphosis (PJK) after long-segment fusion.MethodsModels were established of T11-S1 performing posterior thoracolumbar fusion, different segmental bone cement enhancements and different volume bone cement enhancement to analyze the biomechanical effects of bone cement enhancement on the vertebrae.ResultsIn the single-level cement reinforcement groups, the maximum Mises stress of cancellous bone decreased observably only in the cement-reinforced segment, and the trend of reduction was the same as that of the two-levels group. In the two-level (T10 and T11) cement reinforcement group, the maximum Mises stress of T10 cancellous bone decreased by 17.8%, 17.6%, 7.8%, 6.2%, 21.1% and 7.3%, respectively, and that of T11 cancellous bone decreased by 4.3%, 18.8%, 13.7%, 20.9%, 32.5% and 28.8% under the postures of flexion, extension, lateral bending and axial rotation. Secondly, there was no observable difference in the maximum Mises stress in the vertebral cancellous bone between the 2 ml, 3 ml and 4 ml bone cement models. Furthermore, there was no observable effect of bone cement enhancement of the vertebrae on the intradiscal pressure in adjacent segments.ConclusionThe preventive effect of two-level bone cement-reinforced vertebrae on PJK was better. Secondly, injecting a little cement could reduce vertebral stress and the incidence of leakage.